German patent application No. 23 05 701 discloses a disc brake having brake shoes provided with a noise-damping means. The noise-damping means is made up of a damping element with plastic and elastic properties which is heat resistant, and a cover element in the shape of a metal sheet. The noise-damping means is attached to either the back side of the lining carrier plate or said's tangential frontal end, preferably, by cementing.
Another brake shoe for disc brakes with a noise-damping means is disclosed in WO 92/13210. In this case, the noise-damping means is provided by a damping plate which is attached to the back side of the lining carrier plate.
It has been found that the noise damping provisions known from the above mentioned publications will not achieve a satisfactory result for a brake shoe of a disc brake.
An object of the present invention is to further develop a brake shoe for a spot-type disc brake, in particular for a floating-caliper brake, so that noise damping is improved.
Prior art solutions have not adequately considered the fact that a major part of vibrations which develop noise are produced in a radial direction in a spot-type disc brake, in particular a floating-caliper brake. Therefore, the objective of the basic idea of the present invention is to avoid noise-producing vibrations between the brake shoe or its lining carrier plate, on the one hand, and the brake carrier and/or the brake housing, on the other hand, or to reduce such vibrations to an extent which is insignificant in terms of the development of disturbing noises.
According to the present invention, the lining carrier plate of the brake shoe has a noise-damping layer on its radial contact surfaces towards the brake carrier and/or the brake housing.
In a preferred embodiment of the present invention relating to a brake shoe having a lining carrier plate which carries on its back side a damping plate that is appropriate to damp noise-producing vibrations in the axial or tangential direction, the noise-damping radial layer is a portion of the damping plate which is already provided. The portion is arranged on the corresponding radial contact surface of the lining carrier plate. In a most simple way, a tab-shaped extension which projects from a corresponding edge of the damping plate is bent off in an axial direction of the brake so that this portion of the damping plate abuts directly on the respective radial contact surface of the lining carrier plate.
In a preferred embodiment, the damping plate is attached on the back side of the lining carrier plate by axially projecting pins which extend through corresponding bores in the damping plate and are then riveted, preferably, wobble riveted. This provides a safe attachment of the damping plate on the lining carrier plate which additionally promotes the damping or the suppression of noise-producing vibrations.
For an optimal configuration of the brake shoe, it is recommended that, the portion or portions providing the noise-damping radial layer for the lining carrier plate include(s) an extension which is at least almost at right angles thereto and backgrips the front side of the lining carrier plate. This provision improves the reliability in attachment of the damping plate to the lining carrier plate. In addition, slidability of the lining carrier plate on the brake carrier is improved because the frontal end of the radial layer has no sharp edge which might get hooked on the sliding surface of the brake carrier. Further, the length of the layer in relation to the bent-off extension may be configured and dimensioned so that the respective portion of the damping plate, which is intended for noise damping, is fixed with a certain preload on the lining carrier plate. This prevents the portion of the damping plate from freely swinging outwards and transmitting noise-producing vibrations onto the contact points. The contact points mainly have an only point-shaped or line-shaped design and, thus, are extremely small.